Python 接口自动化测试中的深拷贝与浅拷贝

在编写接口自动化测试脚本时，我们经常需要复制数据结构来模拟不同的测试场景。Python 提供了两种拷贝机制：浅拷贝和深拷贝。理解这两种拷贝的区别对保证测试数据的一致性和准确性至关重要。

浅拷贝 vs 深拷贝

浅拷贝：只复制引用，对于可变对象内部的元素不进行复制。

深拷贝：不仅复制引用，还会复制对象内部的所有元素。‍

拷贝工具

copy 模块：提供了 copy() 和 deepcopy() 函数。

内置函数：如 list.copy() 或 dict.copy()。‍

示例代码

示例 1: 基础列表拷贝

import copyoriginal = [1, 2, 3]shallow_copy = original[:]deep_copy = copy.deepcopy(original)original.append(4)print("Original:", original)print("Shallow copy:", shallow_copy)print("Deep copy:", deep_copy)

输出结果:​​​​​​​

Original: [1, 2, 3, 4]Shallow copy: [1, 2, 3]Deep copy: [1, 2, 3]

示例 2: 列表嵌套列表​​​​​​​

original = [[1, 2], [3, 4]]shallow_copy = copy.copy(original)deep_copy = copy.deepcopy(original)original[0].append(5)print("Original:", original)print("Shallow copy:", shallow_copy)print("Deep copy:", deep_copy)

输出结果:​​​​​​​

Original: [[1, 2, 5], [3, 4]]Shallow copy: [[1, 2, 5], [3, 4]]Deep copy: [[1, 2], [3, 4]]

示例 3: 列表切片拷贝​​​​​​​

original = [1, 2, 3, [4, 5]]shallow_copy = original[:]original[3].append(6)print("Original:", original)print("Shallow copy:", shallow_copy)

输出结果:

Original: [1, 2, 3, [4, 5, 6]]Shallow copy: [1, 2, 3, [4, 5, 6]]

示例 4: 字典拷贝​​​​​​​

original = {'a': 1, 'b': 2}shallow_copy = original.copy()deep_copy = copy.deepcopy(original)original['c'] = 3print("Original:", original)print("Shallow copy:", shallow_copy)print("Deep copy:", deep_copy)

输出结果:​​​​​​​

Original: {'a': 1, 'b': 2, 'c': 3}Shallow copy: {'a': 1, 'b': 2}Deep copy: {'a': 1, 'b': 2}

示例 5: 字典嵌套字典​​​​​​​

original = {'a': 1, 'b': {'c': 2}}shallow_copy = copy.copy(original)deep_copy = copy.deepcopy(original)original['b']['c'] = 3print("Original:", original)print("Shallow copy:", shallow_copy)print("Deep copy:", deep_copy)

输出结果:​​​​​​​

Original: {'a': 1, 'b': {'c': 3}}Shallow copy: {'a': 1, 'b': {'c': 3}}Deep copy: {'a': 1, 'b': {'c': 2}}

示例 6: 自定义对象拷贝​​​​​​​

class MyClass:    def __init__(self, x):        self.x = xoriginal = MyClass([1, 2])shallow_copy = copy.copy(original)deep_copy = copy.deepcopy(original)original.x.append(3)print("Original:", original.x)print("Shallow copy:", shallow_copy.x)print("Deep copy:", deep_copy.x)

输出结果:​​​​​​​

Original: [1, 2, 3]Shallow copy: [1, 2, 3]Deep copy: [1, 2]

示例 7: 元组拷贝​​​​​​​

original = (1, 2, [3, 4])shallow_copy = copy.copy(original)deep_copy = copy.deepcopy(original)original[2].append(5)print("Original:", original)print("Shallow copy:", shallow_copy)print("Deep copy:", deep_copy)

输出结果:​​​​​​​

Original: (1, 2, [3, 4, 5])Shallow copy: (1, 2, [3, 4, 5])Deep copy: (1, 2, [3, 4])

示例 8: 集合拷贝​​​​​​​

original = {1, 2, 3}shallow_copy = copy.copy(original)deep_copy = copy.deepcopy(original)original.add(4)print("Original:", original)print("Shallow copy:", shallow_copy)print("Deep copy:", deep_copy)

输出结果:​​​​​​​

Original: {1, 2, 3, 4}Shallow copy: {1, 2, 3, 4}Deep copy: {1, 2, 3}

示例 9: 多层次嵌套​​​​​​​

original = [1, {'a': 2, 'b': [3, 4]}, 5]shallow_copy = copy.copy(original)deep_copy = copy.deepcopy(original)original[1]['b'].append(5)print("Original:", original)print("Shallow copy:", shallow_copy)print("Deep copy:", deep_copy)

输出结果:​​​​​​​

Original: [1, {'a': 2, 'b': [3, 4, 5]}, 5]Shallow copy: [1, {'a': 2, 'b': [3, 4, 5]}, 5]Deep copy: [1, {'a': 2, 'b': [3, 4]}, 5]

示例 10: 自定义拷贝方法​​​​​​​

class MyClass:    def __init__(self, x):        self.x = x    def custom_copy(self):        return MyClass(self.x[:])original = MyClass([1, 2])shallow_copy = original.custom_copy()original.x.append(3)print("Original:", original.x)print("Shallow copy:", shallow_copy.x)

输出结果:​​​​​​​

Original: [1, 2, 3]Shallow copy: [1, 2]

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